A theoretical study of complex formation, isotope effects, and energy partitioning in the atomic oxygen(1D) + molecular hydrogen(D2, HD) reaction

This paper presents a detailed study of the O(/sup 1/D) + H/sub 2/ ..-->.. OH + H reaction, with an emphasis on how isotope effects probe the mechanism of complex formation and product-state energy partitioning. Most of the results were generated by using quasi-classical trajectories, but the authors also include comparisons using microcanonical statistical theory, phase space theory, and the adiabatic capture/infinite order sudden approximation model. Most of the calculations have used either the recent potential surface of Murrell and Carter (MC) or the one developed by Schinke and Lester (SL). The most important results concern the intramolecular isotope ratio for O + HD, where the authors find that the OD/OH ratio depends strongly on potential surface, with a value of about 1.1 on the MC surface and 1.8 on the SL surfaces. A detailed analysis of the reaction mechanism is performed, and the authors find that the MC isotope ratio is determined by a combination of (1) long-range potential orientation effects that favor collisions at collinear OHD and ODH geometries and (2) formation of a loose complex in which the first-formed bond becomes the product diatomic. The authors have also studied product vibrational and rotational distributions for all fourmore » isotopic reactions. A simple kinematic model is developed for the rotational distributions which indicates that these distributions arise from repulsion between the two hydrogen atoms when the H/sub 2/O complex breaks up.« less